U.S. Pat. No. 6,146,061 discloses a cutting tool in the form of a turning tool, the turning or cutting insert of which is detachably connected to a basic body via a partly resilient (deflectable) tightening screw. In connecting surfaces included in an interface between the cutting insert and the basic body, a number of engagement structures are arranged, which in a mounted state engage each other in order to secure the cutting insert in a predetermined position. The engagement structures are arranged in such a way that a certain displacement of the cutting insert is allowed before the tightening screw is finally tightened. The screw hole in the basic body is eccentrically arranged in relation to the hole in the cutting insert in order to apply a certain bias force to the cutting insert in connection with the tightening of the screw. As a consequence of the eccentricity between the holes in combination with a certain thread play and the elasticity of the screw, the screw affects the cutting insert by two tightening forces acting in different directions, viz., on one hand, a bias force, which acts rectilinearly along the connecting surface of the basic body, and on the other hand a tightening force, which acts straight down into the basic body. By the bias force, the cutting insert is displaced in the direction from a front end of the insert seat until the cutting insert abuts by transverse flank or shoulder surfaces against a pair of rear flank surfaces, which function as stop surfaces. When the cutting insert approaches the final position thereof, the holes are still eccentric, which means that the screw shank upon continued tightening will be somewhat deflected. In such a way, it is ensured that the cutting insert maintains contact with the stop surfaces. However, a problem with this tool is that the screw risks becoming worn out because of, among other things, the biasing of the screw, which may result in a deteriorated clamping of the cutting insert. Another disadvantage with the bias is that the tightening force is not brought straight down into the cutting insert, which results in the tightening force being considerably reduced. Furthermore, in practice the screw lacks capacity to secure the cutting insert in a position in which the active cutting edge of the cutting insert can reliably retain an exact space position in relation to the basic body, since the screw, on one hand, via the male thread thereof, has a certain play in relation to the female thread in the basic body, and on the other hand can be deflected away by the cutting forces.
The present invention aims at managing the above-mentioned problems, and at providing an improved cutting tool. Therefore, an object of the invention is to provide a tool having improved clamping, more precisely by eliminating the need to position the cutting insert in the correct end position directly by the proper tightening screw.
Another object of the invention is to provide a tool that not only locates the cutting insert in the desired way initially in connection with mounting, but also can retain the stable fixation of the cutting insert under the severe stresses encountered by the cutting insert during the chip removing machining.
Yet another object of the invention is to provide a tool having a tightening screw that applies a large, unidirected tightening force to the cutting insert, and has a long service life by not needing to be deflected upon the tightening.